MMSET regulates histone H4K20 methylation and 53BP1 accumulation at DNA damage sites

Area of Science:

• Molecular Biology
• Epigenetics
• DNA Damage Response

Background:

• p53-binding protein 1 (53BP1) is vital for DNA damage response.
• Histone H4 lysine 20 dimethylation (H4K20me2) is critical for 53BP1 recruitment to double-strand breaks (DSBs).
• The precise targeting mechanism of 53BP1 to DSBs, despite stable H4K20me2 levels, remained unclear.

Purpose of the Study:

• To elucidate the mechanism of 53BP1 targeting to DSBs.
• To investigate the role of H4K20 methylation in 53BP1 recruitment.
• To identify the factors responsible for localized H4K20 methylation at DSBs.

Main Methods:

• Induction of DSBs in mammalian cells.
• Analysis of H4K20 methylation levels at DSBs.
• Downregulation of histone methyltransferase MMSET using genetic approaches.
• Investigation of the γH2AX-MDC1 pathway in MMSET recruitment.

Main Results:

• H4K20 methylation increases locally at DSBs.
• The histone methyltransferase MMSET mediates H4K20 methylation at DSBs.
• MMSET downregulation reduces H4K20 methylation and 53BP1 accumulation at DSBs.
• MMSET recruitment to DSBs depends on the γH2AX-MDC1 pathway.

Conclusions:

• A novel pathway involving γH2AX-MDC1-MMSET regulates H4K20 methylation at DSBs.
• This localized H4K20 methylation facilitates 53BP1 recruitment.
• The findings provide new insights into the regulation of DNA damage response pathways.